This little exploit has been around for a while now and not many people know about it. However with the introduction of DF/BF/CoF builds, Apex ring becomes more viable.
The Apex Predator ring gives your pet the access to the passives within all three pet specs (tenacity/ferocity and cunning).
One of the cunning pet passives is Cornered - Spell - World of Warcraft
"When at less than 35% health, your pet does 20% more damage and has a 60% reduced chance to be critically hit."
How would I get my pet under 35% hp though?
Take off all your gear but your trinkets and Apex ring (easily done with an equipment set) and reequip your normal dps set with your ring included.
Your pet will be at 10% hp, use this method a few second prepull.
How long will my pet stay sub 35% hp?
It depends on a number of factors but on avg around 30s, I've seen some instances of it lasting 2.5+ mins though which is a huge dps buff Warcraft Logs - Combat Analysis for Warcraft
(current R3 BM parse on worldbreaker)
You can also use this method prepull, dismiss your pets and put them in the 'call tab' with snapshotted hp.
Perfect for fights like Argus when you're guaranteed to die at least twice and res a new pet everytime.
Or if you have downtime like Eonar/Imonar/Aggra ect